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Post-Landing Orthostatic Intolerance after Spaceflight: Characterization of Intravenous Fluid Resuscitation in NASA Astronauts

A retrospective review of 79 NASA astronauts reveals that post-landing orthostatic intolerance is frequently treated with highly variable, non-standardized intravenous fluid volumes lacking evidence-based guidelines, highlighting an urgent need for physiology-informed protocols for future deep-space missions.

Original authors: Lydia Johnson Kolaparambil Varghese, Josef Pleticha

Published 2026-06-26

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Lydia Johnson Kolaparambil Varghese, Josef Pleticha

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Big Picture: The "Space Hangover"

Imagine you spend six months floating in a zero-gravity pool. Your body gets used to not having to fight gravity. When you finally get back to Earth, your body is like a swimmer who has forgotten how to walk on land. Your blood, which used to float evenly around your body, suddenly gets pulled down by gravity into your legs.

This causes a "space hangover" called Orthostatic Intolerance (OI). It's like standing up too fast after lying down for a long time, but much worse. Astronauts feel dizzy, nauseous, or might even faint.

What the Researchers Did

The authors (Lydia and Josef) acted like detectives looking back at the "case files" of 79 astronauts who returned from the International Space Station between 2001 and 2023. They wanted to see:

How sick were they when they landed?
How did the doctors treat them?
Was there a standard rulebook for the treatment?

What They Found: The Symptoms

When the astronauts landed, many were feeling rough. Think of it like a rough car ride that makes you sick:

39% felt nauseous (like a bad stomach bug).
28% actually vomited.
25% felt dizzy or like the room was spinning.
80% had some kind of balance or inner-ear issue.

The "Who" Matters:

Women were more likely to feel nauseous or lightheaded.
Older astronauts (46–60 years old) were more likely to vomit.

The Treatment: The "IV Fluid" Wild West

This is the most important part of the study. When astronauts got sick, the doctors often gave them IV fluids (saline water dripping into a vein) to "rehydrate" their blood volume.

However, the study found that there was no rulebook. It was a "Wild West" situation:

The Amount: Some astronauts got a tiny cup of water (500 mL), while others got a whole bucket (4,000 mL). It was a huge difference, like one person getting a sip of coffee and another getting a gallon.
The Reason: Sometimes doctors gave fluids because the astronaut's blood pressure was low. But often, they gave fluids even if the blood pressure was normal, or they didn't give fluids even if the blood pressure was low.
The Follow-up: In the real world (like in a hospital), if you give someone fluids, you check their vitals again to see if it worked. In these space landings, doctors rarely wrote down if they checked the astronaut's vitals after giving the fluids.

The Surprising Result:
The researchers tried to find a pattern. They asked: "Did the astronaut get IV fluids because they were vomiting? Or dizzy?"
The answer was: No. There was no clear link. A dizzy astronaut might get fluids, or they might not. A nauseous astronaut might get fluids, or they might not. The decision seemed to depend entirely on the individual doctor's gut feeling at that moment, not on a set of scientific rules.

Why This Matters (According to the Paper)

The paper argues that this "guessing game" works okay for the International Space Station because, when they land, they are immediately surrounded by a full medical team and a hospital.

However, the paper warns that this lack of rules is dangerous for the future. If astronauts go to the Moon or Mars:

They won't have a hospital waiting for them.
They won't have unlimited water or IV bags (every drop counts).
They might have to treat themselves or each other.

If they don't have a clear, science-based rulebook on exactly how much fluid to give and when, they might give too little (and the astronaut stays sick) or too much (wasting precious resources).

The Bottom Line

The study concludes that while we know astronauts get sick after spaceflight, we don't have a standardized way to treat them with IV fluids yet. The current method is inconsistent and relies on guesswork. To prepare for deep space travel, NASA needs to create a clear, science-based guide so that every astronaut gets the right amount of help, every time.

Technical Summary: Post-Landing Orthostatic Intolerance after Spaceflight

Problem Statement
Post-landing orthostatic intolerance (OI) is a ubiquitous clinical consequence for astronauts returning from microgravity to Earth's gravitational field. While up to 30% of astronauts on short-duration missions and nearly 80% on long-duration missions experience symptoms such as lightheadedness, presyncope, and orthostatic hypotension, current management lacks evidence-based standardization. In NASA operations, symptomatic OI is typically treated with intravenous fluids (IVF) and antiemetics at the discretion of flight surgeons. However, indications, dosing strategies, and documentation practices for IVF administration are not standardized, contrasting with terrestrial emergency and perioperative care where fluid resuscitation is guided by defined physiologic targets and serial reassessment. This study addresses the gap in understanding current operational practices to inform the development of structured protocols for future deep-space missions where medical resources will be constrained.

Methodology
The authors conducted a retrospective observational study utilizing de-identified medical documentation from NASA's Lifetime Surveillance of Astronaut Health (LSAH). The cohort consisted of 79 American astronauts (19 female, 60 male) returning from International Space Station missions between 2001 and 2023. The observation window extended from landing (Day 0) through Day 3.

Data were abstracted into five domains:

Symptoms: Nausea, vomiting, dizziness/vertigo, and orthostasis.
Neurovestibular findings.
Hemodynamic abnormalities: Hypotension, hypertension, tachycardia, and bradycardia.
IVF administration: Timing, initial bolus volume, total volume, and number of boluses.
Antiemetic use.

Statistical analyses were primarily descriptive, utilizing chi-square tests and Fisher's exact tests to evaluate associations between demographic characteristics (sex, age, mission duration) and clinical features. Univariable and multivariable logistic regression models were employed to assess which clinical features predicted the receipt of IVF.

Key Results

Symptom Prevalence: Neurovestibular findings were the most common clinical feature, documented in 79.7% of astronauts. Nausea occurred in 39.2%, vomiting in 27.8%, and dizziness or vertigo in 25.3%.
Demographic Associations: Female sex was significantly associated with higher rates of nausea ( $p=0.014$ ) and lightheadedness ( $p=0.033$ ). Older age (46–60 years) was associated with a higher incidence of vomiting ( $p=0.037$ ). No individual symptom significantly predicted the administration of IVF.
IVF Administration Practices: IVF was administered to 41.8% of the cohort (33 of 79 astronauts). There was marked variability in dosing:
- Initial bolus volumes ranged from 500 mL to 4000 mL.
- Median initial bolus was 1350 mL for women and 1000 mL for men.
- Total administered volumes varied widely, with medians of 1850 mL (women) and 1000 mL (men).
Lack of Protocolized Triggers: Hemodynamic triggers (e.g., hypotension, tachycardia) for fluid administration were inconsistently documented. Furthermore, serial reassessment following infusion was rarely recorded. In several instances, IVF was administered despite normal or elevated blood pressure, while some astronauts with documented hemodynamic instability did not receive resuscitation.
Antiemetics: Promethazine was administered to only 10.1% of astronauts and showed no significant association with demographic or clinical variables.

Significance and Claims
The paper asserts that current post-landing management of OI is characterized by substantial heterogeneity and a lack of standardized, physiology-informed protocols. The authors highlight that the absence of evidence-based criteria for fluid resuscitation in spaceflight operations contrasts sharply with terrestrial medical standards.

The significance of these findings is framed primarily around the operational challenges of future exploration missions (e.g., lunar or Martian surface missions). Unlike current Low Earth Orbit (LEO) operations where immediate medical support is available, future missions will require astronauts to ambulate and perform critical tasks shortly after landing with limited medical infrastructure and constrained fluid supplies. The authors argue that without standardized, evidence-based guidelines to guide fluid administration, there is a risk of both under-treatment and over-treatment, which could compromise crew capability and mission safety. Consequently, the study establishes a foundation for developing structured treatment protocols that incorporate wearable sensors, risk stratification, and decision aids to reduce uncertainty in post-landing care.